Mercury in the environment at kodaikanal a high altitude site in south india

Abstract

Mercury concentration in air, water, sediment and fishes were studied at a high altitude location, Kodaikanal, India, to determine the level of contamination and the variations in their temporal distribution. Quantification of the regional background atmospheric Total Gaseous Mercury (TGM) concentration revealed an annual mean concentration of 1.52 ng/m3, which is at the lower end of the mean global background concentration range (1.5 - 2.0 ng/m3). This is the first study in the Indian subcontinent with continuous monitoring of the temporal changes of TGM and its relation to other micrometeorological factors. The variation in mean seasonal concentration of TGM which largely depends on meteorological parameters was significant and found to be in the following order: summer gt winter gt northeast monsoon gt southwest monsoon. The study further revealed that the day time TGM newlineconcentration was strongly modified by solar radiation, evaporation and rainfall. Spatiotemporal variations in Hg distribution in surface and ground waters revealed that the lake water (129.4 ng/L) possesses the highest mean total Hg concentration followed by dam (54.8 ng/L), stream (47.2 ng/L), river (45.1 ng/L) and well water samples (11.6 ng/L). The annual mean total mercury concentration of surface sediment at the study locations was recorded to be 115.9 ng/g dry weight, ranging between 2.8 and 517.3 ng/g with strong seasonal variations. The higher enrichment factors of the sediment clearly reflect the influence of anthropogenic activities. The total Hg concentrations (ng/g dry weight) in the muscle of two commercially important fishes found in the lakes within the study area ranged between 5 and 115 ng/g with a mean concentration of 34.1 ± 29.9 ng/g. The present study confirmed that the levels of Hg concentration in the studied fishes are within safe limits and hence, the fish may be considered safe for human consumption. newline newline